WO2008032188A2 - Method and apparatus for calibrating the gain and the offset of a plurality of cylinder pressure sensors of an internal combustion engine - Google Patents

Method and apparatus for calibrating the gain and the offset of a plurality of cylinder pressure sensors of an internal combustion engine Download PDF

Info

Publication number
WO2008032188A2
WO2008032188A2 PCT/IB2007/002633 IB2007002633W WO2008032188A2 WO 2008032188 A2 WO2008032188 A2 WO 2008032188A2 IB 2007002633 W IB2007002633 W IB 2007002633W WO 2008032188 A2 WO2008032188 A2 WO 2008032188A2
Authority
WO
WIPO (PCT)
Prior art keywords
cylinder pressure
output characteristic
pressure sensor
cylinder
output
Prior art date
Application number
PCT/IB2007/002633
Other languages
French (fr)
Other versions
WO2008032188A3 (en
Inventor
Shigeki Miyashita
Mitsuyuki Kobayashi
Original Assignee
Toyota Jidosha Kabushiki Kaisha
Denso Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Toyota Jidosha Kabushiki Kaisha, Denso Corporation filed Critical Toyota Jidosha Kabushiki Kaisha
Publication of WO2008032188A2 publication Critical patent/WO2008032188A2/en
Publication of WO2008032188A3 publication Critical patent/WO2008032188A3/en

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
    • F02D41/2425—Particular ways of programming the data
    • F02D41/2429—Methods of calibrating or learning
    • F02D41/2451—Methods of calibrating or learning characterised by what is learned or calibrated
    • F02D41/2474—Characteristics of sensors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D35/00—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for
    • F02D35/02—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions
    • F02D35/023—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions by determining the cylinder pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/04—Introducing corrections for particular operating conditions
    • F02D41/12—Introducing corrections for particular operating conditions for deceleration
    • F02D41/123—Introducing corrections for particular operating conditions for deceleration the fuel injection being cut-off
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L23/00—Devices or apparatus for measuring or indicating or recording rapid changes, such as oscillations, in the pressure of steam, gas, or liquid; Indicators for determining work or energy of steam, internal-combustion, or other fluid-pressure engines from the condition of the working fluid
    • G01L23/22—Devices or apparatus for measuring or indicating or recording rapid changes, such as oscillations, in the pressure of steam, gas, or liquid; Indicators for determining work or energy of steam, internal-combustion, or other fluid-pressure engines from the condition of the working fluid for detecting or indicating knocks in internal-combustion engines; Units comprising pressure-sensitive members combined with ignitors for firing internal-combustion engines
    • G01L23/221—Devices or apparatus for measuring or indicating or recording rapid changes, such as oscillations, in the pressure of steam, gas, or liquid; Indicators for determining work or energy of steam, internal-combustion, or other fluid-pressure engines from the condition of the working fluid for detecting or indicating knocks in internal-combustion engines; Units comprising pressure-sensitive members combined with ignitors for firing internal-combustion engines for detecting or indicating knocks in internal combustion engines
    • G01L23/225—Devices or apparatus for measuring or indicating or recording rapid changes, such as oscillations, in the pressure of steam, gas, or liquid; Indicators for determining work or energy of steam, internal-combustion, or other fluid-pressure engines from the condition of the working fluid for detecting or indicating knocks in internal-combustion engines; Units comprising pressure-sensitive members combined with ignitors for firing internal-combustion engines for detecting or indicating knocks in internal combustion engines circuit arrangements therefor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L27/00—Testing or calibrating of apparatus for measuring fluid pressure
    • G01L27/002—Calibrating, i.e. establishing true relation between transducer output value and value to be measured, zeroing, linearising or span error determination
    • G01L27/005—Apparatus for calibrating pressure sensors

Definitions

  • a control apparatus for an internal combustion engine which has a cylinder pressure sensor that is capable of detecting the cylinder pressure provided in each cylinder of an internal combustion engine. This control apparatus corrects variation in the combustion states and the like among the cylinders based on the cylinder pressure (i.e., the combustion pressure) detected while the engine is operating.
  • the relationship between the actual pressure in a cylinder detected by the cylinder pressure sensor and the output from the cylinder pressure sensor of that cylinder i.e., the output characteristic
  • the output characteristic may change over time, variation in the output characteristics among the cylinder pressure sensors may also occur with use.
  • JP-A-63-268955 corrects variation in the output of a cylinder pressure sensor by simultaneously measuring the combustion pressure of a single given cylinder using two cylinder pressure sensors.
  • the apparatus described in JP-A-63-268955 is structured such that a cylinder pressure sensor is arranged in a portion of a cylinder head that is between cylinders, for example, and each cylinder pressure sensor is connected to the cylinders on both sides of it via a pressure introduction passage that can be opened and closed. Accordingly, the cylinder pressure sensor arranged between the cylinders can be selectively connected to the cylinders on both sides of it such that the pressures in the cylinders on both sides can be measured with a single sensor.
  • JP-A-63-268955 two sensors arranged on both sides, i.e., one sensor on either side, of a given cylinder are simultaneously connected to that cylinder while the engine is operating. As a result, the peak value of the pressure in a single cylinder is simultaneously measured by two cylinder pressure sensors.
  • JP-A-63-268955 corrects the output characteristic of one sensor such that the peak values (the average value of the number of cycles) measured by the two sensors as described above match. This peak value correction is then successively repeated for adjacent sensors until the output characteristics for all of the cylinder pressure sensors ultimately match.
  • JP-A- 1-262348 describes technology in which an intake pressure sensor that detects the intake pressure of the engine is provided in addition to a cylinder pressure sensor. The output characteristic of each cylinder pressure sensor is corrected based on the output from the intake pressure sensor. That is, the technology described in JP-A- 1-262348 detects the cylinder pressure at a predetermined timing during the intake stroke when combustion is not being performed in a cylinder, such as during cranking or during a fuel cut when decelerating or the like, using the cylinder pressure sensor provided in each cylinder.
  • JP-A- 1-262348 further detects the intake pressure of the engine using the intake pressure sensor, and corrects the offset of the output characteristics of the cylinder pressure sensors (i.e., the cylinder pressure when the output from the sensor is zero) such that the cylinder pressure during the intake stroke of each cylinder that was detected by the cylinder pressure sensor as described above matches the intake pressure of the engine that was detected by the intake pressure sensor.
  • the output characteristics of the cylinder pressure sensors are made to match by correcting the offset and gain of the output characteristics of the cylinder pressure sensors using the intake pressure sensor.
  • the apparatus described in JP-A- 1-262348 requires that the intake pressure sensor be provided in order to correct the variation in the output characteristics of the sensors. Therefore, the output characteristics of the cylinder pressure sensors is unable to be corrected in an engine that is not provided with an intake pressure sensor.
  • This invention thus provides a control apparatus and a control method for an internal combustion engine, which enables variation in the output characteristics of a plurality of cylinder pressure sensors to be accurately corrected with a simple structure without requiring an intake pressure sensor or a pressure introduction passage that connects two cylinders with a cylinder pressure sensor, or the like.
  • the reference output characteristic may be the output characteristic of one of the cylinder pressure sensors other than the at least one cylinder pressure sensor.
  • the reference output characteristic may be a predetermined output characteristic of a cylinder pressure sensor according to the operating condition of the engine.
  • the predetermined output characteristic of the cylinder pressure sensor may be the output characteristic of a different cylinder pressure sensor than a cylinder pressure sensor that is to be corrected.
  • the predetermined operating condition may be set based on at least an engine speed and an intake air amount.
  • the reference output characteristic may be set based on an average value of the offset of the output characteristic before the correction of the at least one cylinder pressure sensors and an average value of the gain of the output characteristic before the correction of the at least one cylinder pressure sensors.
  • the gain of the output characteristic of each sensor i.e., the slope of the straight line of the output characteristic
  • the offset i.e., the pressure when the output is zero
  • the output characteristics of the sensors can be accurately made to match with a simple structure without adding extra structure such as an intake pressure sensor in order to correct the output characteristics of the cylinder pressure sensors.
  • the output characteristic of a cylinder pressure sensor of one cylinder may be obtained and used as the common reference value used for the rest of the sensors in the correction, and the output characteristics of the cylinder pressure sensors of the other cylinders may be corrected so that they match the output characteristic of the cylinder pressure sensor of that one cylinder.
  • the first detection timing from among the two predetermined detection timings may be a timing at which the cylinder pressure of each cylinder peaks.
  • the peak values (the pressure at top dead center of the compression stroke during a fuel cut, for example) of the cylinder pressures substantially match in all of the cylinders. Therefore, according to the foregoing structure, the output characteristics can be corrected with extreme accuracy by using the peak value of the cylinder pressure to correct the output characteristic.
  • the second detection timing from among the two predetermined detection timings may be set to be during an intake stroke of the cylinder.
  • the cylinder pressures substantially match during the intake stroke so the accuracy of the output characteristic correction is improved by correcting the output characteristics of the sensors using the cylinder pressure during the intake stroke.
  • the second detection timing from among the two predetermined detection timings may be set to be during an exhaust stroke of the cylinder.
  • the cylinder pressures substantially match during the exhaust stroke so the accuracy of the output characteristic correction is improved by correcting the output characteristics of the sensors vising the cylinder pressure during the exhaust stroke.
  • an average value of detection values for a predetermined number of cycles of each of the two detection timings may be used as a detection value of the cylinder pressure sensor output at the two predetermined detection timings.
  • a second aspect of the invention relates to a control method for an internal combustion engine having a cylinder pressure sensor that detects a cylinder pressure and is provided in each of a plurality of cylinders.
  • the control method corrects an output characteristic of at least one cylinder pressure sensor, from among the plurality of cylinder pressure sensors.
  • the output characteristic being indicative of a relationship between an output of the at least one cylinder pressure sensor and the cylinder pressure, and being based on cylinder pressures and outputs of the at least one cylinder pressure sensor at two predetermined detection timings during a stroke cycle of a cylinder under a predetermined operating condition.
  • the output characteristic is a linear function of the cylinder pressure sensor output and the cylinder pressure; and the correction is made by correcting an offset and a gain of the output characteristic of the at least one cylinder pressure sensor such that the output characteristic of the at least one cylinder pressure sensor matches a common reference output characteristic that is stored in advance.
  • a correction that eliminates variation in the output characteristics of cylinder pressure sensors can be performed with a simple structure.
  • FIG. 4 is a graph illustrating a method for correcting variation in the output characteristics of the cylinder pressure sensors according to the invention
  • FIG. 5 is a flowchart illustrating a first example embodiment of a routine for correcting variation in the output characteristics of cylinder pressure sensors according to the invention
  • FIG. 6 is a flowchart illustrating a second example embodiment of a routine for correcting variation in the output characteristics of cylinder pressure sensors according to the invention
  • FIG. 7 is a flowchart illustrating a third example embodiment of a routine for correcting variation in the output characteristics of cylinder pressure sensors according to the invention.
  • FIG. 1 is a block diagram schematically showing an example embodiment in which the invention has been applied to an internal combustion engine of a vehicle.
  • the vehicular internal combustion engine of a vehicle.
  • the vehicular internal combustion engine of a vehicle.
  • internal combustion engine 10 shown in FIG. 1 is a spark-ignition engine having four cylinders denoted as #1 to #4.
  • Each cylinder #1 to #4 is provided with a cylinder pressure sensor 11 to 14, respectively, capable of detecting the cylinder pressure, i.e., the pressure in the cylinder.
  • the cylinder pressure sensors 11 to 14 are a known type of pressure sensor that uses a piezoelectric element or the like. Any one of various types of cylinder pressure sensors can be used as the cylinder pressure sensors of this example embodiment.
  • a type of cylinder pressure sensor can be used that is arranged in the cylinder block or the cylinder head and communicated via a connection hole to the inside of the cylinder, or a washer type cylinder pressure sensor can be used that is mounted on a spark plug, not shown, in each cylinder.
  • an electronic control unit (ECU) 30 is formed of a known type of microcomputer which, in addition to performing basic engine control such as fuel injection control and spark timing control of the engine 10, also performs control to make the combustion state in the cylinders uniform (hereinafter referred to as "uniformity control") as well as makes a correction to eliminate variation in the output characteristics of the cylinder pressure sensors 11 to 14 in order to achieve a uniform combustion state in the cylinders, as will be described later.
  • the ECU 30 functions as a control portion.
  • the ECU 30 receives various signals, including a signal indicative of the output voltage from the cylinder pressure sensors 11 to 14 via an AD converter, not shown, a pulse signal indicative of the crankshaft rotation angle CA of the engine from a crankshaft angle sensor 31 arranged near a crankshaft of the engine 10, and a signal indicative of the intake air flowrate of the engine from an airflow meter 33 provided in an intake passage of the engine 10.
  • the ECU 30 sets the engine fuel injection quantity and the engine spark timing based on the engine speed and the flowrate of the intake air of the engine detected by the airflow meter 33. Because the fuel injection quantity and the spark timing can each be calculated by a known method, detailed descriptions of these calculations will be omitted here.
  • FIG. 2 is a graph showing the output characteristic, i.e., relationship between the output of the cylinder pressure sensor and the cylinder pressure, of a typical cylinder pressure sensor.
  • the vertical axis (i.e., the y-axis) in the drawing represents the pressure and the horizontal axis (i.e., the x-axis) in the drawing represents the cylinder pressure sensor output.
  • the output of the cylinder pressure sensor increases substantially proportionately with the pressure so the output characteristic is a straight line.
  • the point of intersection of the straight line of the output characteristic with the y-axis (i.e., the cylinder pressure at which the cylinder pressure sensor output is zero) will be referred to as the offset and the slope of the straight line of the output characteristic will be referred to as the gain.
  • a reference output characteristic (shown by the alternate long and short dash line in FIG. 4) is set according to a method which will be described later, and the actual output characteristic (shown by the solid line in FIG. 4) is corrected to match this reference output characteristic.
  • two groups of data are produced, one for the actual output of a cylinder pressure sensor and another for the pressure corresponding to that output of the cylinder pressure sensor.
  • the gain a and the offset b of the actual output characteristic of the cylinder pressure sensor are calculated based on this data.
  • the y-axis represents the pressure
  • the x-axis represents the cylinder pressure sensor output
  • the output characteristic is expressed with y (i.e., the pressure) as a function of x (i.e., the sensor output).
  • y i.e., the pressure
  • x i.e., the sensor output
  • the first example embodiment of the invention relates to the correction of the output characteristic when an output characteristic of the cylinder pressure sensor of a given cylinder is used as the reference output characteristic.
  • the output characteristic (gain and offset) of each cylinder is obtained by the method described above.
  • the output characteristic of one of those cylinders is used as the reference output characteristic and the output characteristic of the other cylinders are made to match that reference output characteristic.
  • FIG. 5 is a flowchart illustrating a routine for correcting the output characteristic of a cylinder pressure sensor according to this example embodiment. This routine is executed by the ECU 30.
  • step S501 in FIG. 5 it is determined whether a condition to correct the output characteristic of a cylinder pressure sensor (this condition may hereinafter also be referred to as "correction execution condition") is satisfied.
  • the output characteristic is corrected only when a fuel cut is being performed in the engine. This is because during a fuel cut, combustion does not occur in the cylinders so there is no variation in the pressures in the cylinders that occurs due to variation in combustion, e.g., the peak values of the pressures in the cylinders match better than they do at any other time.
  • step S501 If it is determined in step S501 that a fuel cut is currently being performed, then the actual cylinder pressure is measured in step S503 using the cylinder pressure sensors at two detection timings set beforehand during the stroke cycle of each cylinder.
  • the two detection timings at which the measurements are taken are 1) at the point when the cylinder pressure peaks (i.e., TDC of the combustion stroke), and 2) within a predetermined period during the exhaust stroke (or intake stroke).
  • a cylinder internal peak pressure (Pp) and an average pressure (Pe) of the cylinder pressure within the predetermined period during the exhaust stroke (or intake stroke) are obtained. That is, the calculation accuracy of the output characteristic that is calculated as described below is improved by using the minimum and maximum values of the cylinder pressure.
  • measurements may be taken over a plurality of cycles (such as 10 cycles) and the average values of the measurement values Pp and Pe of the two timings as well as the average values of the cylinder pressure sensor outputs Vp and Ve at that time may be used as Pp, Pe, Vp, and Ve.
  • the average values prevents the measurement value from being effected by noise.
  • a second example embodiment of the invention relates to the case in which a reference output characteristic set in advance according to the operating conditions is used.
  • the reference output characteristic is set beforehand according to an operating state (such as speed and intake air amount) of the engine.
  • the reference output characteristic used according to the engine speed and intake air amount during a fuel cut is selected.
  • the cylinder pressure during the intake stroke (or the exhaust stroke) and the peak value of the cylinder pressure are to a large extent always the same values if the engine speed and the intake air amount are set.
  • the reference output characteristic is prepared in advance from the cylinder pressure during the intake stroke or the exhaust stroke and the peak value of the cylinder pressure according to the engine speed and the intake air amount using the cylinder pressure sensor that has been corrected. Then the variation in the output characteristics of the cylinder pressure sensors can be eliminated and the pressure values detected by the cylinder pressure sensors can be made closer to the true values by selecting the reference output characteristic according to the operating state while the engine is actually operating and correcting the output characteristics of the cylinder pressure sensors.
  • the cylinder pressure sensor that has been corrected corresponds to different cylinder pressure sensor of the invention.
  • FIG. 6 is a flowchart illustrating a routine for correcting the output characteristic of a cylinder pressure sensor according to this second example embodiment, and corresponds to FIG. 5 of the first example embodiment.
  • Steps S601, S603, and S605 in FIG. 6 are the same as steps S501, S503, and S505 in FIG. 5, respectively.
  • the output characteristic is corrected only when a fuel cut is being performed (step S601). Then, the peak value of the cylinder pressure during the fuel cut and the average cylinder pressure during a predetermined period of the exhaust stroke (or the intake stroke) during the fuel cut are measured for a plurality of cycles using the cylinder pressure sensors, and the peak value Pp and the cylinder pressure Pe during the exhaust stroke (or the intake stroke) are calculated as cycle average values for each cylinder (step S603). The output characteristic (i.e., the gain a and the offset b) of each cylinder pressure sensor is then calculated using these (step S605).
  • the gain A and the offset B of a reference output characteristic that was set in advance is then read according to the current engine speed and the intake air amount.
  • the reference output characteristic for each operating state is obtained based on the actual measurement value of the cylinder pressure when the engine was operating with each combination of engine speed and intake air amount. That gain A and offset B are then stored in the ROM of the ECU 30 with the engine speed and the intake air amount as parameters.
  • the corresponding data from the gain A and the offset B stored in the ROM are read according to the engine speed and the intake air amount.
  • step S609 the output characteristic of each cylinder pressure sensor is corrected using the gain A and the offset B of the reference output characteristic read as described above. This operation is the same as the operation in step S507 in FIG. 5 so a description thereof will be omitted.
  • a third example embodiment of the invention relates to a case in which the average of the output characteristics of the cylinder pressure sensors of all of the cylinders is used as the reference output characteristic.
  • the average values of the output characteristics (average values of the gain a and the offset b of each output characteristic) of all of the cylinder pressure sensors are obtained after the output characteristics of the cylinder pressure sensors have been calculated, and these average values are used as the gain A and the offset B of the reference output characteristic.
  • FIG. 7 is a flowchart illustrating a routine for correcting the output characteristic of a cylinder pressure sensor according to this third example embodiment. and is similar to FIG. 5 of the first example embodiment and FIG. 6 of the second example embodiment.
  • Steps S701, S703, and S705 in the routine shown in FIG. 7 are the same as steps S501 , S503, and S505 in the routine shown in FIG. 5, and are used to calculate the gain a and the offset b of the output characteristic of each cylinder pressure sensor.
  • step S707 the average values A and B of the gain a and the offset b, respectively, of all of the cylinder pressure sensors that were obtained as described above are calculated in step S707.
  • step S709 the output characteristic of each cylinder pressure sensor is corrected using the average values A and B of the gain and offset that were calculated in this way as the gain and offset of the reference output characteristic.
  • the operation in step S709 is the same as the operation in step S507 in FIG. 5 and the operation in step S609 in FIG. 6.
  • the output characteristics of the cylinder pressure sensors can be made to match while preventing the pressure value detected by the cylinder pressure sensors from being very far off from the true pressure value.
  • the output characteristic of the cylinder pressure sensor is obtained with the pressure value as a function of the cylinder pressure sensor output.
  • the exact same correction as in the foregoing example embodiments can also be made when the output characteristic is obtained with the cylinder pressure sensor output as a function of the pressure value instead.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Abstract

A control apparatus for an internal combustion engine is provided with a cylinder pressure sensor (11 to 14) in each cylinder of an engine (10). The control apparatus performs a correction to eliminate variation in output characteristics of the cylinder pressure sensors when controlling the combustion states of the cylinders based on the detected cylinder pressures so that the combustion states are uniform. In this correction, the output characteristic of each cylinder pressure sensor is expressed as a linear function, and the gain and offset of the output characteristic of a cylinder pressure sensor is corrected such that the output characteristic of each cylinder pressure sensor matches a common reference output characteristic that was set in advance.

Description

CONTROLAPPARATUS AND CONTROL METHOD FORAN INTERNAL
COMBUSTION ENGINE
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The invention relates to a control apparatus and a control method for an internal combustion engine. More particularly, the invention relates to a control apparatus and a control method for an internal combustion engine, which controls the engine based on the combustion pressure in a cylinder which is detected by a cylinder pressure sensor.
2. Description of the Related Art
[0002] A control apparatus for an internal combustion engine is known which has a cylinder pressure sensor that is capable of detecting the cylinder pressure provided in each cylinder of an internal combustion engine. This control apparatus corrects variation in the combustion states and the like among the cylinders based on the cylinder pressure (i.e., the combustion pressure) detected while the engine is operating.
[0003] However, when a cylinder pressure sensor is arranged in each cylinder and the pressure in each cylinder is detected individually in this way, variation in the output characteristics among the cylinders becomes a problem.
[0004] That is, the relationship between the actual pressure in a cylinder detected by the cylinder pressure sensor and the output from the cylinder pressure sensor of that cylinder (i.e., the output characteristic) initially varies somewhat for each cylinder pressure sensor. Also, because the output characteristic may change over time, variation in the output characteristics among the cylinder pressure sensors may also occur with use.
[0005] When variation occurs in the output characteristics among the sensors in this way, there appears to be variation in the combustion states of the cylinders obtained based on the output from the cylinder pressure sensors even when there is not and the combustion state in each cylinder is ideal and the same. In this case, a variation correction is performed to eliminate the apparent variation in the combustion states of the cylinders, and as a result, the correction actually causes variation to occur in a case where initially there was none.
[0006] Therefore, Japanese Patent Application Publication No. 63-268955 (JP-A-63-268955) and Japanese Patent Application Publication No. 1-262348 (JP-A- 1-262348), for example, propose methods for correcting variation in the output characteristics of cylinder pressure sensors when a cylinder pressure sensor is provided in each of a plurality of cylinders.
[0007] For example, the technology described in JP-A-63-268955 corrects variation in the output of a cylinder pressure sensor by simultaneously measuring the combustion pressure of a single given cylinder using two cylinder pressure sensors.
[0008] That is, the apparatus described in JP-A-63-268955 is structured such that a cylinder pressure sensor is arranged in a portion of a cylinder head that is between cylinders, for example, and each cylinder pressure sensor is connected to the cylinders on both sides of it via a pressure introduction passage that can be opened and closed. Accordingly, the cylinder pressure sensor arranged between the cylinders can be selectively connected to the cylinders on both sides of it such that the pressures in the cylinders on both sides can be measured with a single sensor.
[0009] In JP-A-63-268955, two sensors arranged on both sides, i.e., one sensor on either side, of a given cylinder are simultaneously connected to that cylinder while the engine is operating. As a result, the peak value of the pressure in a single cylinder is simultaneously measured by two cylinder pressure sensors.
[0010] Also, the technology described in JP-A-63-268955 corrects the output characteristic of one sensor such that the peak values (the average value of the number of cycles) measured by the two sensors as described above match. This peak value correction is then successively repeated for adjacent sensors until the output characteristics for all of the cylinder pressure sensors ultimately match.
[0011] Also, JP-A- 1-262348 describes technology in which an intake pressure sensor that detects the intake pressure of the engine is provided in addition to a cylinder pressure sensor. The output characteristic of each cylinder pressure sensor is corrected based on the output from the intake pressure sensor. That is, the technology described in JP-A- 1-262348 detects the cylinder pressure at a predetermined timing during the intake stroke when combustion is not being performed in a cylinder, such as during cranking or during a fuel cut when decelerating or the like, using the cylinder pressure sensor provided in each cylinder.
[0012] The technology described in JP-A- 1-262348 further detects the intake pressure of the engine using the intake pressure sensor, and corrects the offset of the output characteristics of the cylinder pressure sensors (i.e., the cylinder pressure when the output from the sensor is zero) such that the cylinder pressure during the intake stroke of each cylinder that was detected by the cylinder pressure sensor as described above matches the intake pressure of the engine that was detected by the intake pressure sensor.
[0013] The technology described in JP-A- 1-262348 also calculates a theoretical value of the cylinder pressure at top dead center (TDC) of the compression stroke for each cylinder by multiplying the compression ratio of the engine by the intake pressure detected by the intake pressure sensor, as well as detects, using the cylinder pressure sensors, the actual pressure (peak value) at TDC of the compression stroke in each cylinder provided that combustion is not being performed in the cylinder, and corrects the gain of the output characteristics of the cylinder pressure sensors (i.e., the slope of a straight line indicative of the relationship between the output from the cylinder pressure sensor and the cylinder pressure) such that these peak values come to match the theoretical value.
[0014] Accordingly, in the apparatus described in JP-A-I -262348, the offset and the gain are corrected such that the output characteristics of the sensors match. [0015] With the apparatus described in JP-A-63-268955, one cylinder pressure sensor needs to be connected to two cylinders, which restricts the arrangement of the cylinder pressure sensor and requires that a pressure introduction passage be provided that connects the cylinder pressure sensor with the two cylinders. As a result, the structure of the apparatus becomes complex. [0016] Further, with the apparatus described in JP-A-63-268955, only a correction based on the peak value of the cylinder pressure of each cylinder is performed which still leaves the variation in the offset of the output characteristics of the cylinder pressure sensors. Therefore, variation in the output characteristics of the sensors can not be completely eliminated.
[0017] Meanwhile, with the apparatus described in JP-A- 1-262348, the output characteristics of the cylinder pressure sensors are made to match by correcting the offset and gain of the output characteristics of the cylinder pressure sensors using the intake pressure sensor. [0018] However, the apparatus described in JP-A- 1-262348 requires that the intake pressure sensor be provided in order to correct the variation in the output characteristics of the sensors. Therefore, the output characteristics of the cylinder pressure sensors is unable to be corrected in an engine that is not provided with an intake pressure sensor.
SUMMARY OF THE INVENTION
[0019] This invention thus provides a control apparatus and a control method for an internal combustion engine, which enables variation in the output characteristics of a plurality of cylinder pressure sensors to be accurately corrected with a simple structure without requiring an intake pressure sensor or a pressure introduction passage that connects two cylinders with a cylinder pressure sensor, or the like.
[0020] A first aspect of the invention relates to a control apparatus for an internal combustion engine having a cylinder pressure sensor that detects a cylinder pressure and is provided in each of a plurality of cylinders. This control apparatus corrects an output characteristic of at least one cylinder pressure sensor, from among the plurality of cylinder pressure sensors. The output characteristic being indicative of a relationship between an output of the at least one cylinder pressure sensor and the cylinder pressure, and being based on cylinder pressures and outputs of the at least one cylinder pressure sensor at two predetermined detection timings during a stroke cycle of a cylinder under a predetermined operating condition. With this control apparatus, the output characteristic is a linear function of the cylinder pressure sensor output and the cylinder pressure; and the correction is made by correcting an offset and a gain of the output characteristic of the at least one cylinder pressure sensor such that the output characteristic of the at least one cylinder pressure sensor matches a common reference output characteristic that is stored in advance.
[0021] In this structure, the reference output characteristic may be the output characteristic of one of the cylinder pressure sensors other than the at least one cylinder pressure sensor.
[0022] In this structure, the reference output characteristic may be a predetermined output characteristic of a cylinder pressure sensor according to the operating condition of the engine.
[0023] In this structure, the predetermined output characteristic of the cylinder pressure sensor may be the output characteristic of a different cylinder pressure sensor than a cylinder pressure sensor that is to be corrected.
[0024] In this structure, the predetermined operating condition may be set based on at least an engine speed and an intake air amount.
[0025] In the first aspect, the reference output characteristic may be set based on an average value of the offset of the output characteristic before the correction of the at least one cylinder pressure sensors and an average value of the gain of the output characteristic before the correction of the at least one cylinder pressure sensors.
[0026] In the foregoing structure, the gain of the output characteristic of each sensor (i.e., the slope of the straight line of the output characteristic) and the offset (i.e., the pressure when the output is zero) are obtained using the cylinder pressure sensor output at two detection timings that is detected under the same conditions in each cylinder. Then a correction is made such that the gain and the offset match respective reference values.
[0027] These reference values are not necessarily related to the actual pressure (i.e., the intake pressure) as they are in JP-A-I -262348 described above. Instead, they are set only for the purpose of making the output characteristics of the sensors match.
[0028] That is, if the actual cylinder pressures are detected by separate means and the output characteristic of each sensor is corrected using those pressures as the reference values, as is the case with the technology described in JP-A- 1-262348, then not only do the output characteristics of the sensors match, but the outputs of the sensors indicate the actual cylinder pressures.
[0029] However, in actuality, when a correction to eliminate variation in the combustion states of the cylinders is made using cylinder pressure sensors, it is important that the output characteristics of the cylinder pressure sensors match and that there is no variation among them. However, because of these output characteristics match, the output values calculated from the cylinder pressure sensor outputs do not necessarily have to strictly match the true pressure.
[0030] According to the foregoing structure, the output characteristics of the sensors are made to match using a common reference value (which does not necessarily have to be based on the true pressure) for the cylinder pressure sensors which is stored in advance. Therefore, although there is a possibility that the cylinder pressure detected by each cylinder may be a value that is somewhat different than the true cylinder pressure, the output characteristics of the sensors all match so variation in the combustion states of the cylinders can be accurately detected.
[0031] Therefore, according to the foregoing structure, the output characteristics of the sensors can be accurately made to match with a simple structure without adding extra structure such as an intake pressure sensor in order to correct the output characteristics of the cylinder pressure sensors. [0032] Also, the output characteristic of a cylinder pressure sensor of one cylinder, for example, may be obtained and used as the common reference value used for the rest of the sensors in the correction, and the output characteristics of the cylinder pressure sensors of the other cylinders may be corrected so that they match the output characteristic of the cylinder pressure sensor of that one cylinder. Alternatively or in addition, a reference output characteristic may be set beforehand according to the operating state (e.g., engine load and engine speed) of the engine, and the output characteristics of the cylinder pressure sensors of the cylinders may be corrected to match this reference output characteristic. [0033] Also, an average value of the output characteristic (offset and gain) of the cylinder pressure sensors of the cylinders that was obtained under a predetermined condition may also be used as the reference value.
[0034] In the foregoing structure, the predetermined operating condition may be a condition in which a fuel cut is being performed. [0035] According to this structure, the output characteristics of the cylinder pressure sensors are corrected during a fuel cut such as when the engine is decelerating. During a fuel cut there is no variation in the cylinder pressure due to variation in combustion because combustion does not take place. Therefore, at the time the output characteristics of the cylinder pressure sensors are corrected, the cylinder pressures are substantially the same so the output characteristics can be corrected accurately.
[0036] In the foregoing structure, the first detection timing from among the two predetermined detection timings may be a timing at which the cylinder pressure of each cylinder peaks.
[0037] For example, under an operating condition in which there is little variation in cylinder pressure, such as during a fuel cut, the peak values (the pressure at top dead center of the compression stroke during a fuel cut, for example) of the cylinder pressures substantially match in all of the cylinders. Therefore, according to the foregoing structure, the output characteristics can be corrected with extreme accuracy by using the peak value of the cylinder pressure to correct the output characteristic. [0038] In the foregoing structure, the second detection timing from among the two predetermined detection timings may be set to be during an intake stroke of the cylinder.
[0039] According to this structure, the cylinder pressures substantially match during the intake stroke so the accuracy of the output characteristic correction is improved by correcting the output characteristics of the sensors using the cylinder pressure during the intake stroke.
[0040] In the foregoing structure, the second detection timing from among the two predetermined detection timings may be set to be during an exhaust stroke of the cylinder.
[0041] According to this structure, the cylinder pressures substantially match during the exhaust stroke so the accuracy of the output characteristic correction is improved by correcting the output characteristics of the sensors vising the cylinder pressure during the exhaust stroke. [0042] In the foregoing structure, an average value of detection values for a predetermined number of cycles of each of the two detection timings may be used as a detection value of the cylinder pressure sensor output at the two predetermined detection timings.
[0043] According to the foregoing structure, the effect from measurement error due to noise and the like can be reduced.
[0044] A second aspect of the invention relates to a control method for an internal combustion engine having a cylinder pressure sensor that detects a cylinder pressure and is provided in each of a plurality of cylinders. The control method corrects an output characteristic of at least one cylinder pressure sensor, from among the plurality of cylinder pressure sensors. The output characteristic being indicative of a relationship between an output of the at least one cylinder pressure sensor and the cylinder pressure, and being based on cylinder pressures and outputs of the at least one cylinder pressure sensor at two predetermined detection timings during a stroke cycle of a cylinder under a predetermined operating condition. In this control method for an internal combustion engine, the output characteristic is a linear function of the cylinder pressure sensor output and the cylinder pressure; and the correction is made by correcting an offset and a gain of the output characteristic of the at least one cylinder pressure sensor such that the output characteristic of the at least one cylinder pressure sensor matches a common reference output characteristic that is stored in advance. [0045] According to this aspect, a correction that eliminates variation in the output characteristics of cylinder pressure sensors can be performed with a simple structure.
BRIEF DESCRIPTION OF DRAWINGS
[0046] The foregoing and further objects, features and advantages of the invention will become apparent from the following description of example embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:
FIG. 1 is a block diagram schematically showing an example of an internal combustion engine of a vehicle to which the invention has been applied;
FIG. 2 is a graph showing the output characteristic of a typical cylinder pressure sensor; FIG. 3 is a graph showing the variation in the output characteristics of typical cylinder pressure sensors;
FIG. 4 is a graph illustrating a method for correcting variation in the output characteristics of the cylinder pressure sensors according to the invention;
FIG. 5 is a flowchart illustrating a first example embodiment of a routine for correcting variation in the output characteristics of cylinder pressure sensors according to the invention;
FIG. 6 is a flowchart illustrating a second example embodiment of a routine for correcting variation in the output characteristics of cylinder pressure sensors according to the invention; and FIG. 7 is a flowchart illustrating a third example embodiment of a routine for correcting variation in the output characteristics of cylinder pressure sensors according to the invention.
DETAILED DESCRIPTION OF EMBODIMENTS [0047] In the following description and the accompanying drawings, the present invention will be described in more detail in terms of example embodiments.
[0048] FIG. 1 is a block diagram schematically showing an example embodiment in which the invention has been applied to an internal combustion engine of a vehicle. In this example embodiment, the vehicular internal combustion engine
(hereinafter simply referred to as "internal combustion engine" or simply "engine") 10 shown in FIG. 1 is a spark-ignition engine having four cylinders denoted as #1 to #4.
[0049] Each cylinder #1 to #4 is provided with a cylinder pressure sensor 11 to 14, respectively, capable of detecting the cylinder pressure, i.e., the pressure in the cylinder.
[0050] In this example embodiment, the cylinder pressure sensors 11 to 14 are a known type of pressure sensor that uses a piezoelectric element or the like. Any one of various types of cylinder pressure sensors can be used as the cylinder pressure sensors of this example embodiment. For example, a type of cylinder pressure sensor can be used that is arranged in the cylinder block or the cylinder head and communicated via a connection hole to the inside of the cylinder, or a washer type cylinder pressure sensor can be used that is mounted on a spark plug, not shown, in each cylinder.
[0051] In the example embodiment, an electronic control unit (ECU) 30 is formed of a known type of microcomputer which, in addition to performing basic engine control such as fuel injection control and spark timing control of the engine 10, also performs control to make the combustion state in the cylinders uniform (hereinafter referred to as "uniformity control") as well as makes a correction to eliminate variation in the output characteristics of the cylinder pressure sensors 11 to 14 in order to achieve a uniform combustion state in the cylinders, as will be described later. The ECU 30 functions as a control portion.
[0052] In order to execute these controls, the ECU 30 receives various signals, including a signal indicative of the output voltage from the cylinder pressure sensors 11 to 14 via an AD converter, not shown, a pulse signal indicative of the crankshaft rotation angle CA of the engine from a crankshaft angle sensor 31 arranged near a crankshaft of the engine 10, and a signal indicative of the intake air flowrate of the engine from an airflow meter 33 provided in an intake passage of the engine 10.
[0053] Also, an output port of the ECU 30 is connected to a spark circuit 41 and a fuel injection circuit 43 by which the ECU 30 controls the spark timing and the fuel injection of the engine 10.
[0054] The ECU 30 calculates the engine speed N (rpm) from the frequency of the pulse signal input from the crank angle sensor 31. and also calculates the crankshaft rotation angle from the number of crank angle pulses after a reference position signal, which is generated separately every time the piston reaches top dead center (TDC) of the combustion stroke in a specific cylinder (such as cylinder #1), is input.
[0055] Also, the ECU 30 sets the engine fuel injection quantity and the engine spark timing based on the engine speed and the flowrate of the intake air of the engine detected by the airflow meter 33. Because the fuel injection quantity and the spark timing can each be calculated by a known method, detailed descriptions of these calculations will be omitted here.
[0056] In this example embodiment, the ECU 30 also calculates combustion parameters such as the total amount of heat generated (i.e., the total heat generation quantity) during combustion in each cylinder and the indicated mean effective pressure based on the output voltage from the cylinder pressure sensors 11 to 14 at each crank angle. The ECU 30 also performs uniformity control to make the combustion states in the cylinders uniform by correcting the spark timing and the fuel injection quantity calculated as described above to eliminate any variation in those combustion parameters of the cylinders. [0057] This uniformity control itself can be performed according to any one of various known methods. However, it is not possible to make the combustion states of the cylinders uniform with any of these methods if there is variation in the output characteristics of the cylinder pressure sensors of the cylinders.
[0058] FIG. 2 is a graph showing the output characteristic, i.e., relationship between the output of the cylinder pressure sensor and the cylinder pressure, of a typical cylinder pressure sensor. The vertical axis (i.e., the y-axis) in the drawing represents the pressure and the horizontal axis (i.e., the x-axis) in the drawing represents the cylinder pressure sensor output. [0059] As shown in FIG. 2, the output of the cylinder pressure sensor increases substantially proportionately with the pressure so the output characteristic is a straight line. In this specification, the point of intersection of the straight line of the output characteristic with the y-axis, (i.e., the cylinder pressure at which the cylinder pressure sensor output is zero) will be referred to as the offset and the slope of the straight line of the output characteristic will be referred to as the gain.
[0060] Therefore, using the gain a and the offset b, the output characteristic can be expressed as y = ax + b.
[0061] In actuality, however, there are cases in which there is not only initial variation in the values of the gain a and the offset b that is within the tolerance levels with each sensor, but also variation in the values of the gain a and the offset b that occurs over time and with use. When a plurality of cylinder pressure sensors are used, variation ends up occurring in the pressure detection values.
[0062] For example, FIG. 3 shows, in frame format, variation in the output characteristics of the cylinder pressure sensors 11 to 14 shown in FIG. 1. In FIG. 3, roman numerals I to IV denote the output characteristics of the sensors 11 to 14, respectively.
[0063] As shown in FIG. 3, when there is variation in the output characteristics of the cylinder pressure sensors, even in an ideal state in which there is absolutely no variation in the combustion states of the cylinders, the outputs of the cylinder pressure sensors of the cylinders would differ so the indicated mean effective pressure and the total amount of heat generated and the like calculated based on the output of the cylinder pressure sensors would end up being different. In this case, if the foregoing uniformity control is performed, it may conversely end up causing variation in the combustion states of the cylinders. [0064] Therefore, in this example embodiment, variation in the output characteristics of the cylinder pressure sensors is corrected by the method described below. FlG. 4 illustrates this method for correcting variation in the output characteristics
(hereinafter also referred to as the "output characteristic variation correction method"), and corresponds to FIG. 2.
[0065] In this example embodiment, a reference output characteristic (shown by the alternate long and short dash line in FIG. 4) is set according to a method which will be described later, and the actual output characteristic (shown by the solid line in FIG. 4) is corrected to match this reference output characteristic. [0066] More specifically, first, two groups of data are produced, one for the actual output of a cylinder pressure sensor and another for the pressure corresponding to that output of the cylinder pressure sensor. The gain a and the offset b of the actual output characteristic of the cylinder pressure sensor are calculated based on this data.
[0067] For example, assuming that the cylinder pressure sensor outputs are xe and xp when the actual cylinder pressures measured by the sensor are ye and yp, the gain a and the offset b of the output characteristic of this cylinder pressure sensor can be obtained by Expressions (1) and Expression (2) below. a = (yp - ye) / (xp - xe) ... (1) b = (ye x xp - yp x xe) / (xp - xe) ... (2) [0068] In order to make this output characteristic match the reference output characteristic indicated by the alternate long and short dash line in FIG. 4, when the gain of the reference output characteristic is designated as A and the offset of the reference output characteristic is designated as B, it is only necessary to multiply a correction coefficient α = A / a by the gain a of the actual output characteristic and add a correction coefficient β = (B - b) to the offset of the actual output characteristic.
[0069] Therefore, the output characteristic after the correction can be obtained according to Expression (3) below. y = α χ (a χ χ) + b + β ... (3)
[0070] Incidentally, in the descriptions of FIG. 2 to FIG. 4, the y-axis represents the pressure, the x-axis represents the cylinder pressure sensor output, and the output characteristic is expressed with y (i.e., the pressure) as a function of x (i.e., the sensor output). However, conversely, it is also possible to make the same correction by having the y-axis represent the sensor output and having the x-axis represent the pressure, and expressing the output characteristic with the sensor output (y) as a function of the pressure (x).
[0071] Next, the reference output characteristic in FIG. 4 will be described. As described above, in the invention priority is simply given to eliminating variation in the output characteristics of the cylinder pressure sensors, so the output characteristics are not corrected using, for example, a cylinder pressure that is measured separately. Therefore, the cylinder pressure that was calculated using the output characteristic after the correction may not always strictly match the actual pressure.
[0072] Accordingly, it is preferable to use a value that corresponds as much as possible to the truest pressure as the reference output characteristic used for the correction such that not only will the output characteristic of each cylinder pressure sensor after the correction match, but also the pressure value obtained using the output characteristic after the correction will be as close to the true pressure as possible.
[0073] Therefore, in the following example embodiment, three examples of output characteristic corrections will be described in detail, i.e., (1) an output characteristic correction when an output characteristic of a cylinder pressure sensor of a given cylinder is used as the reference output characteristic, (2) an output characteristic correction when an output characteristic that was set in advance according to the operating conditions is used as the reference output characteristic, and (3) an output characteristic correction when an average output characteristic of the cylinder pressure sensors of all the cylinders is used as the reference output characteristic.
[0074] The first example embodiment of the invention relates to the correction of the output characteristic when an output characteristic of the cylinder pressure sensor of a given cylinder is used as the reference output characteristic. In this example embodiment, the output characteristic (gain and offset) of each cylinder is obtained by the method described above. The output characteristic of one of those cylinders is used as the reference output characteristic and the output characteristic of the other cylinders are made to match that reference output characteristic.
[0075] Originally, there is not much variation or deviation in the output characteristics of the cylinder pressure sensors. Therefore, by making the output characteristics of the other cylinder pressure sensors match the output characteristic of the one cylinder pressure sensor, it is possible to eliminate variation in the output characteristics of the cylinder pressure sensors without the output value detected by each cylinder pressure sensor being off much from the true value. [0076] FIG. 5 is a flowchart illustrating a routine for correcting the output characteristic of a cylinder pressure sensor according to this example embodiment. This routine is executed by the ECU 30.
[0077] In step S501 in FIG. 5, it is determined whether a condition to correct the output characteristic of a cylinder pressure sensor (this condition may hereinafter also be referred to as "correction execution condition") is satisfied. In this example embodiment, the output characteristic is corrected only when a fuel cut is being performed in the engine. This is because during a fuel cut, combustion does not occur in the cylinders so there is no variation in the pressures in the cylinders that occurs due to variation in combustion, e.g., the peak values of the pressures in the cylinders match better than they do at any other time.
[0078] If it is determined in step S501 that a fuel cut is currently being performed, then the actual cylinder pressure is measured in step S503 using the cylinder pressure sensors at two detection timings set beforehand during the stroke cycle of each cylinder. [0079] In this example embodiment, the two detection timings at which the measurements are taken are 1) at the point when the cylinder pressure peaks (i.e., TDC of the combustion stroke), and 2) within a predetermined period during the exhaust stroke (or intake stroke). As a result, a cylinder internal peak pressure (Pp) and an average pressure (Pe) of the cylinder pressure within the predetermined period during the exhaust stroke (or intake stroke) are obtained. That is, the calculation accuracy of the output characteristic that is calculated as described below is improved by using the minimum and maximum values of the cylinder pressure.
[0080] Also, instead of using only the measurement values obtained by measuring only once at the two timings as described above, measurements may be taken over a plurality of cycles (such as 10 cycles) and the average values of the measurement values Pp and Pe of the two timings as well as the average values of the cylinder pressure sensor outputs Vp and Ve at that time may be used as Pp, Pe, Vp, and Ve. Using the average values prevents the measurement value from being effected by noise. [0081] Once the measurements have been taken by all of the cylinder pressure sensors, the gain a and the offset b of each cylinder pressure sensor from the foregoing expressions are calculated in step S505 according to Expression (4) and Expression (5), respectively, using the measurement values (or the average values of those measurement values) Pp and Pe of the two timings described above for each cylinder, and the cylinder pressure sensor outputs (or the average values of those outputs) Vp and Ve at that time, a = (Pp - Pe) / (Vp - Ve) ... (4) b = (Pe x Vp - Pp x Ve) / (Vp - Ve) ... (5)
After the gain a and the offset b of each cylinder have been obtained in this way, the correction coefficient α = A / a and the correction coefficient β = (B - b) described above are obtained for each cylinder in step S507, respectively, using the gain and the offset, which were calculated in the manner described above, for a cylinder pressure sensor of an arbitrary cylinder (such as cylinder #1) from among the cylinders as reference values A and B. Then the correction routine ends.
[0082] Once the correction coefficients α and β have been obtained from this routine, the ECU 30 corrects the output characteristic of each cylinder pressure sensor using these correction coefficients and obtains the cylinder pressure as P = α x (a χ V) + b + β, where P is the cylinder pressure and V is the output of the sensor.
[0083] Accordingly, variation in the output characteristics of the cylinder pressure sensors is corrected so it is possible to accurately make the combustion states in the cylinders uniform using the cylinder pressures obtained by the cylinder pressure sensors.
[0084] A second example embodiment of the invention relates to the case in which a reference output characteristic set in advance according to the operating conditions is used. In this example embodiment, the reference output characteristic is set beforehand according to an operating state (such as speed and intake air amount) of the engine. In this example embodiment, the reference output characteristic used according to the engine speed and intake air amount during a fuel cut is selected.
[0085] As described above, variation in the cylinder pressure during the intake stroke (or the exhaust stroke) and the peak value of the cylinder pressure in each cylinder is less because combustion does not take place while a fuel cut is being performed.
Also, the cylinder pressure during the intake stroke (or the exhaust stroke) and the peak value of the cylinder pressure (i.e., the pressure at TDC of the compression stroke) are to a large extent always the same values if the engine speed and the intake air amount are set.
[0086] Accordingly, the reference output characteristic is prepared in advance from the cylinder pressure during the intake stroke or the exhaust stroke and the peak value of the cylinder pressure according to the engine speed and the intake air amount using the cylinder pressure sensor that has been corrected. Then the variation in the output characteristics of the cylinder pressure sensors can be eliminated and the pressure values detected by the cylinder pressure sensors can be made closer to the true values by selecting the reference output characteristic according to the operating state while the engine is actually operating and correcting the output characteristics of the cylinder pressure sensors. Here, the cylinder pressure sensor that has been corrected corresponds to different cylinder pressure sensor of the invention.
[0087] FIG. 6 is a flowchart illustrating a routine for correcting the output characteristic of a cylinder pressure sensor according to this second example embodiment, and corresponds to FIG. 5 of the first example embodiment.
[0088] Steps S601, S603, and S605 in FIG. 6 are the same as steps S501, S503, and S505 in FIG. 5, respectively.
[0089] That is, in this example embodiment as well, the output characteristic is corrected only when a fuel cut is being performed (step S601). Then, the peak value of the cylinder pressure during the fuel cut and the average cylinder pressure during a predetermined period of the exhaust stroke (or the intake stroke) during the fuel cut are measured for a plurality of cycles using the cylinder pressure sensors, and the peak value Pp and the cylinder pressure Pe during the exhaust stroke (or the intake stroke) are calculated as cycle average values for each cylinder (step S603). The output characteristic (i.e., the gain a and the offset b) of each cylinder pressure sensor is then calculated using these (step S605).
[0090] In this example embodiment, the gain A and the offset B of a reference output characteristic that was set in advance is then read according to the current engine speed and the intake air amount. As described above, in this example embodiment, the reference output characteristic for each operating state is obtained based on the actual measurement value of the cylinder pressure when the engine was operating with each combination of engine speed and intake air amount. That gain A and offset B are then stored in the ROM of the ECU 30 with the engine speed and the intake air amount as parameters. In step S607, the corresponding data from the gain A and the offset B stored in the ROM are read according to the engine speed and the intake air amount. [0091] In step S609, the output characteristic of each cylinder pressure sensor is corrected using the gain A and the offset B of the reference output characteristic read as described above. This operation is the same as the operation in step S507 in FIG. 5 so a description thereof will be omitted.
[0092] A third example embodiment of the invention relates to a case in which the average of the output characteristics of the cylinder pressure sensors of all of the cylinders is used as the reference output characteristic. When the output characteristics are corrected in this example embodiment, the average values of the output characteristics (average values of the gain a and the offset b of each output characteristic) of all of the cylinder pressure sensors are obtained after the output characteristics of the cylinder pressure sensors have been calculated, and these average values are used as the gain A and the offset B of the reference output characteristic.
[0093] That is, in the first example embodiment described above, the calculated output characteristic of a given cylinder pressure sensor is used as the reference output characteristic and the output characteristics of all of the cylinder pressure sensors are made to match this output characteristic. In contrast, in the third example embodiment, the average output characteristic of all of the cylinder pressure sensors, instead of the output characteristic of one cylinder pressure sensor, is used as the reference output characteristic. [0094] FIG. 7 is a flowchart illustrating a routine for correcting the output characteristic of a cylinder pressure sensor according to this third example embodiment. and is similar to FIG. 5 of the first example embodiment and FIG. 6 of the second example embodiment.
[0095] Steps S701, S703, and S705 in the routine shown in FIG. 7 are the same as steps S501 , S503, and S505 in the routine shown in FIG. 5, and are used to calculate the gain a and the offset b of the output characteristic of each cylinder pressure sensor.
[0096] Next, in this example embodiment, the average values A and B of the gain a and the offset b, respectively, of all of the cylinder pressure sensors that were obtained as described above are calculated in step S707. [0097] Then in step S709, the output characteristic of each cylinder pressure sensor is corrected using the average values A and B of the gain and offset that were calculated in this way as the gain and offset of the reference output characteristic. The operation in step S709 is the same as the operation in step S507 in FIG. 5 and the operation in step S609 in FIG. 6. [0098] As a result, in this third example embodiment as well, the output characteristics of the cylinder pressure sensors can be made to match while preventing the pressure value detected by the cylinder pressure sensors from being very far off from the true pressure value.
[0099] Incidentally, in the example embodiments described above, the output characteristic of the cylinder pressure sensor is obtained with the pressure value as a function of the cylinder pressure sensor output. However, the exact same correction as in the foregoing example embodiments can also be made when the output characteristic is obtained with the cylinder pressure sensor output as a function of the pressure value instead.
[0100] While the invention has been described with reference to example embodiments thereof, it is to be understood that the invention is not limited to the example embodiments or constructions. To the contrary, the invention is intended to cover various modifications and equivalent arrangements. In addition, while the various elements of the example embodiments are shown in various combinations and configurations, which are exemplary, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the invention.

Claims

CLAIMS:
1. A control apparatus for an internal combustion engine having a cylinder pressure sensor that detects a cylinder pressure and is provided in each of a plurality of cylinders, the control apparatus correcting an output characteristic of at least one cylinder pressure sensor, from among the plurality of cylinder pressure sensors, the output characteristic being indicative of a relationship between an output of the at least one cylinder pressure sensor and the cylinder pressure, and being based on cylinder pressures and outputs of the at least one cylinder pressure sensor at two predetermined detection timings during a stroke cycle of a cylinder under a predetermined operating condition, the control apparatus characterized in that: the output characteristic is a linear function of the cylinder pressure sensor output and the cylinder pressure; and the correction is made by correcting an offset and a gain of the output characteristic of the at least one cylinder pressure sensor such that the output characteristic of the at least one cylinder pressure sensor matches a common reference output characteristic that is stored in advance.
2. The control apparatus according to claim 1 , wherein the reference output characteristic is the output characteristic of one of the cylinder pressure sensors other than the at least one cylinder pressure sensor.
3. The control apparatus according to claim 1, wherein the reference output characteristic is a predetermined output characteristic of a cylinder pressure sensor according to the operating condition of the engine.
4. The control apparatus according to claim 3, wherein the predetermined output characteristic of the cylinder pressure sensor is the output characteristic of a different cylinder pressure sensor than a cylinder pressure sensor that is to be corrected.
5. The control apparatus according to claim 3 or 4, wherein the predetermined operating condition is set based on at least an engine speed and an intake air amount.
6. The control apparatus according to claim 1, wherein the reference output characteristic is set based on an average value of the offset of the output characteristic before the correction of the at least one cylinder pressure sensors and an average value of the gain of the output characteristic before the correction of the at least one cylinder pressure sensors.
7. The control apparatus according to any one of claims 1 to 6, wherein the predetermined operating condition is a condition in which a fuel cut is being performed.
8. The control apparatus according to any one of claims 1 to 7, wherein the first detection timing from among the two predetermined detection timings is a timing at which the cylinder pressure of each cylinder peaks.
9. The control apparatus according to any one of claims 1 to 8, wherein the second detection timing from among the two predetermined detection timings is set to be during an intake stroke of the cylinder.
10. The control apparatus according to any one of claims 1 to 8, wherein the second detection timing from among the two predetermined detection timings is set to be during an exhaust stroke of the cylinder.
11. The control apparatus according to any one of claims 1 to 10, wherein an average value of detection values for a predetermined number of cycles of each of the two detection timings is used as a detection value of the cylinder pressure sensor output at the two predetermined detection timings.
12. A control method for an internal combustion engine having a cylinder pressure sensor that detects a cylinder pressure and is provided in each of a plurality of cylinders, the control method correcting an output characteristic of at least one cylinder pressure sensor, from among the plurality of cylinder pressure sensors, the output characteristic being indicative of a relationship between an output of the at least one cylinder pressure sensor and the cylinder pressure, and being based on cylinder pressures and outputs of the at least one cylinder pressure sensor at two predetermined detection timings during a stroke cycle of a cylinder under a predetermined operating condition, the control method characterized in that: the output characteristic is a linear function of the cylinder pressure sensor output and the cylinder pressure; and the correction is made by correcting an offset and a gain of the output characteristic of the at least one cylinder pressure sensor such that the output characteristic of the at least one cylinder pressure sensor matches a common reference output characteristic that is stored in advance.
13. A control apparatus for an internal combustion engine, comprising: a cylinder pressure sensor which detects a cylinder pressure and is provided in each of a plurality of cylinders; and a control portion that corrects an output characteristic of at least one cylinder pressure sensor, from among the plurality of cylinder pressure sensors, the output characteristic being indicative of a relationship between an output of the at least one cylinder pressure sensor and the cylinder pressure, and being based on cylinder pressures and outputs of the at least one cylinder pressure sensor at two predetermined detection timings during a stroke cycle of a cylinder under a predetermined operating condition, wherein the output characteristic is a linear function of the cylinder pressure sensor output and the cylinder pressure, and the control portion corrects an offset and a gain of the output characteristic of the at least one cylinder pressure sensor such that the output characteristic of the at least one cylinder pressure sensor matches a common reference output characteristic that is stored in advance.
PCT/IB2007/002633 2006-09-14 2007-09-13 Method and apparatus for calibrating the gain and the offset of a plurality of cylinder pressure sensors of an internal combustion engine WO2008032188A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2006249504A JP2008069714A (en) 2006-09-14 2006-09-14 Control device of internal combustion engine
JP2006-249504 2006-09-14

Publications (2)

Publication Number Publication Date
WO2008032188A2 true WO2008032188A2 (en) 2008-03-20
WO2008032188A3 WO2008032188A3 (en) 2008-05-22

Family

ID=39047838

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2007/002633 WO2008032188A2 (en) 2006-09-14 2007-09-13 Method and apparatus for calibrating the gain and the offset of a plurality of cylinder pressure sensors of an internal combustion engine

Country Status (3)

Country Link
JP (1) JP2008069714A (en)
CN (1) CN101449140A (en)
WO (1) WO2008032188A2 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2908022A3 (en) * 2013-11-26 2016-08-24 Hyundai Motor Company Offset correction method for automobile oil pressure sensor

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5000584B2 (en) * 2008-05-20 2012-08-15 本田技研工業株式会社 Current sensor
JP5000585B2 (en) * 2008-05-20 2012-08-15 本田技研工業株式会社 Current sensor
CN103348119A (en) * 2010-06-11 2013-10-09 丰田自动车株式会社 Control device for internal combustion engine
KR101534712B1 (en) * 2013-12-17 2015-07-08 현대자동차 주식회사 Method and system for diagnosing and correcting boost pressure sensor and air flow sensor by signal of combustion pressure sensor
KR101855067B1 (en) * 2014-12-22 2018-06-25 바르실라 핀랜드 오이 A method of calibrating a cylinder pressure sensor and an internal combustion piston engine
CN104879228B (en) * 2015-06-12 2019-02-12 潍柴动力股份有限公司 A kind of null offset adaptive approach of engine pressure sensor
FR3047072B1 (en) * 2016-01-21 2018-01-26 Continental Automotive France METHOD AND DEVICE FOR PROCESSING A SIGNAL PROVIDED BY A PRESSURE MEASURING SENSOR REGENERATING IN A CYLINDER
US10215112B1 (en) * 2017-09-08 2019-02-26 GM Global Technology Operations LLC Method and system for controlling an internal combustion engine
CN113933060B (en) * 2021-09-08 2023-11-17 东风越野车有限公司 Method and equipment for measuring zero reference angle of diesel engine

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5105896A (en) * 1991-03-05 1992-04-21 Caterpillar Inc. Dynamic payload monitor
JP2002242750A (en) * 2001-02-14 2002-08-28 Honda Motor Co Ltd Cylinder internal pressure detecting device for internal combustion engine
EP1731890A1 (en) * 2005-06-09 2006-12-13 Ford Global Technologies, LLC Method and apparatus for calibrating the gain of a cylinder pressure sensor of an internal combustion engine

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5105896A (en) * 1991-03-05 1992-04-21 Caterpillar Inc. Dynamic payload monitor
JP2002242750A (en) * 2001-02-14 2002-08-28 Honda Motor Co Ltd Cylinder internal pressure detecting device for internal combustion engine
EP1731890A1 (en) * 2005-06-09 2006-12-13 Ford Global Technologies, LLC Method and apparatus for calibrating the gain of a cylinder pressure sensor of an internal combustion engine

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2908022A3 (en) * 2013-11-26 2016-08-24 Hyundai Motor Company Offset correction method for automobile oil pressure sensor

Also Published As

Publication number Publication date
JP2008069714A (en) 2008-03-27
WO2008032188A3 (en) 2008-05-22
CN101449140A (en) 2009-06-03

Similar Documents

Publication Publication Date Title
WO2008032188A2 (en) Method and apparatus for calibrating the gain and the offset of a plurality of cylinder pressure sensors of an internal combustion engine
US5090199A (en) Apparatus for controlling air-fuel ratio for engine
US7909018B2 (en) Control for determining a firing timing of an internal-combustion engine
JP5543134B2 (en) Method and controller for calibrating a fuel injector of an internal combustion engine, program and storage medium
JP4353220B2 (en) Fuel injection control device for internal combustion engine
US7386388B2 (en) Air-fuel ratio control system and method for internal combustion engine, and engine control unit
US7484405B2 (en) System and method for engine sound calibration
US7668687B2 (en) Systems and methods for compensating pressure sensor errors
US5247910A (en) Air-fuel ratio control apparatus
US20070192015A1 (en) Engine torque estimating device
KR102372257B1 (en) Method for diagnosing misfires of an internal combustion engine
JP5072203B2 (en) Measuring method of combustion chamber pressure
JP5381755B2 (en) In-cylinder pressure sensor output correction device
WO2013069157A1 (en) Intra-cylinder pressure sensor fault diagnostic device and intra-cylinder sensor sensitivity correction device provided with same
EP1854980B1 (en) In-cylinder pressure detection device and method for internal combustion engine
US20110238279A1 (en) Diagnosis for multiple cylinder engine
JP4747977B2 (en) In-cylinder pressure sensor calibration device
JP5482718B2 (en) Engine compatible equipment
JP4347997B2 (en) Internal combustion engine control method and apparatus
US6840236B2 (en) Engine control device
EP1593825B1 (en) Method to balance the cylinders of a combustion engine with sensors for each cylinder
JP3979704B2 (en) In-cylinder pressure measuring device
JP4340577B2 (en) In-cylinder pressure sensor temperature detection device, in-cylinder pressure detection device using the same, and control device for internal combustion engine
JP6543509B2 (en) Control device for internal combustion engine
JP5737205B2 (en) In-cylinder pressure sensor abnormality diagnosis device

Legal Events

Date Code Title Description
WWE Wipo information: entry into national phase

Ref document number: 200780014463.1

Country of ref document: CN

121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 07825099

Country of ref document: EP

Kind code of ref document: A2

WWE Wipo information: entry into national phase

Ref document number: 2007825099

Country of ref document: EP

WD Withdrawal of designations after international publication

Designated state(s): EP

NENP Non-entry into the national phase in:

Ref country code: DE